1. Field of the Invention
The present invention generally relates to the art of inspecting products to determine the acceptability thereof and, more particularly, to a seal inspecting machine for successively inspecting bagged products to check if each bagged product is completely sealed.
2. Description of the Prior Art
Bagged products each containing one or more articles such as, for example, snacks or candies are generally inspected to determine if each bagged product is completely sealed. This is particularly true where the articles in the bagged products are susceptible to degradation or decay and the presence or absence of an insufficient or defective seal in the bag is therefore desired, or highly recommended, to be discovered before the bagged products are shipped to the market. Seal inspection hitherto performed is carried out by applying from above a pressure to each of the bagged product by means of a pressure applicator. In other words, if the bagged product is properly completely sealed, a gaseous medium such as, for example, air or inert gas filled within the bagged product will not leak outside even when the pressure is applied thereto from above, and the pressure applicator applying the pressure to the bagged product therefore receives a predetermined reactive force from the bagged product. So long as the pressure applicator receives the predetermined reactive force from the bagged product being pressed, the strokes of movement of the pressure applicator and/or the pressing reactive force of the pressure applicator do not vary. On the other hand, if the bagged product is not properly sealed, the gaseous medium within the bagged product leaks outside when the pressure is applied thereto by means of the pressure applicator, with the bagged product consequently deflated, resulting in variation of the stroke of movement of the pressure applicator and/or the pressing reactive force of the pressure applicator. Thus, by checking the variation of the stroke of movement of the pressure applicator and/or the pressing reactive force of the pressure applicator that may take place when the pressure is applied to the bagged product from above, the presence or absence of the incomplete seal in each of the bagged product can be determined.
A seal inspecting machine operable in the manner described above is disclosed in, for example, the Japanese Laid-open Patent Publication No. 8-169424. According to this publication, the seal inspecting machine is equipped with a device for detecting beforehand the presence of a defect in a sealed container while the sealed container during transport thereof by means of a belt unit is pressed from above. The detecting device includes a force sensor disposed above the belt unit at a predetermined location for outputting a signal indicative of a reactive force based on the internal pressure of air within the container when the latter is pressed, so that when the output attains a value lower than a predetermined value the container can be determined having a defective seal.
However, it has been found the prior art seal inspecting machine has a problem in that it requires the unnecessary use of the specially designed detecting device including the force sensor, resulting in increase of the cost required to install the seal inspecting machine. Also, since the upper and lower belts are spaced a predetermined distance from each other, the height of containers which the prior art inspecting machine can handle is limited. Accordingly, the prior art seal inspecting machine has an additional problem in that where the containers of varying height are successively transported, the spacing between the upper and lower belts has to be readjusted to accommodate the varying height of the containers.
Accordingly, the present invention has been devised with a view to substantially eliminating the above discussed problems inherent in the prior art seal inspecting machine and has for its essential object to provide an improved seal inspecting machine effective to perform a seal inspection subject to bagged products in an efficient and inexpensive manner.
In order to accomplish the foregoing object, the present invention is featured in that the seal inspecting machine is so constructed as follows.
The seal inspecting machine is of a type capable of performing a seal inspection subject to bagged products by means of a pressing action, and includes a presser unit for pressing the respective bagged product, said presser unit capable of being selectively moved in a direction close towards and away from the bagged product, and a servo motor for detecting a reactive force acting on the presser unit or a displacement of the presser unit. The presser unit is driven by the servo motor in the direction close towards and away from the bagged product.
Preferably, the seal inspecting machine further includes a transport means for transporting the bagged products successively and a detecting means for detecting a delivery of each of the bagged products onto the transport means. The presser unit cooperates with the transport means to transport the bagged product and is operable in response to a detection signal from the detecting means to press the bagged product.
Also preferably, the seal inspecting machine further includes a control parameter storage means for storing control parameters that are used when the presser unit is moved by the servo motor, and a control means for reading the control parameters from the storage means and operable to actuate the servo motor with the read-out control parameters.
In addition to the use of the transport means and the detecting means, the seal inspecting machine may include a product specifying means for specifying the bagged products to be inspected. The control parameter storage means stores the control parameters for each of the bagged products and the control means actuates the servo motor based on the control parameters corresponding to the bagged product specified by the specifying means.
The seal inspecting machine may furthermore include a product characteristic detecting means for automatically detecting characteristics of each of the bagged products delivered one at a time before seal inspection, and a control parameter setting means for setting the control parameters based on the characteristics of each of the bagged product detected by the detecting means. In this case, the control parameter storage means stores the parameters that have been set by the control parameter setting means.
According to the present invention, each time the bagged product is delivered, the servo motor causes the presser unit to move towards the bagged product and then to press it, seal inspection is possible of any kind of the bagged products regardless of the height of the bagged product.
Also, since the servo motor itself detects the reactive force acting on the presser unit or the displacement of the presser unit when the bagged product is pressed by the presser unit, no special equipment such as a pressure sensor and/or a displacement sensor is needed. Accordingly, the seal inspection to determine the presence or absence of a seal abnormality in the bagged product can efficiently carried out with inexpensive facilities.
According to a preferred embodiment of the present invention, the seal inspecting machine also includes the transport means for transporting the bagged products successively and the detecting means for detecting delivery of the bagged products one at a time. Since the presser unit cooperates the transport means to transport each of the bagged product, each time the bagged product is detected by the detecting means, the bagged product is sandwiched between the presser unit and the transport means with the presser unit pressing the bagged product so that the seal inspection can be performed while the bagged product is transported. Accordingly, the efficiency of seal inspection can be increased and can further be increased if used in combination with various packaging machines, weighing apparatuses and/or transport apparatuses.
Where each time the bagged products are delivered one at a time onto the transport conveyor, the presser unit is activated to move relative to the respective bagged product to press the latter, it is important to consider how the amount of movement of the presser unit effected by the servo motor as well as the timing at which the movement of the presser unit is initiated is to be controlled in dependence on the bagged product.
In view of the foregoing, according to one preferred embodiment of the present invention, the seal inspecting machine is also provided with a control parameter storage means for storing control parameters that are used when the presser unit is moved by the servo motor, and a control means for reading the control parameters from the storage means and operable to actuate the servo motor with the read-out control parameters. Therefore, when change occurs in the bagged products to be delivered onto the intermediate transport conveyor, the control parameters stored in the storage means are read out and are utilized to set operating conditions of the servo motor. This makes it possible to eliminate any possible intervention of a human error to thereby increase the reliability of the machine-based seal inspection. It is to be noted that the control parameters referred to above includes the limit reactive force, the initial height of the presser unit, the limit height of the presser unit, the descend start time for the presser unit, the elevation start time for the presser unit, the data capture start time, and the data capture end time.
In one preferred embodiment of the present invention, in addition to the use of the transport means and the detecting means, the seal inspecting machine is also provided with a product specifying means for specifying the bagged products to be inspected, such that the control parameter storage means stores the control parameters for each of the bagged products and the control means actuates the servo motor based on the control parameters corresponding to the bagged product specified by the specifying means. Accordingly, by specifying the bagged products using, for example, product identification numbers, it is possible to accurately and quickly set the operating conditions of the servo motor by reading the control parameters stored in the storage means. Accordingly, it is possible to accomplish a quick seal inspection accompanied by increase of the efficiency of inspection.
Again according to one preferred embodiment of the present invention, seal inspecting machine is furthermore provided with a product characteristic detecting means for automatically detecting characteristics of each of the bagged products delivered one at a time before seal inspection, and a control parameter setting means for setting the control parameters based on the characteristics of each of the bagged product detected by the detecting means. In this case, the control parameter storage means stores the parameters that have been set by the control parameter setting means. Accordingly, there is no need to input and set the control parameters for the servo motor for each of the bagged products, making it possible to achieve an automation of the seal inspection. It is to be noted that the. characteristics of the bagged product may include the length of the bagged product, the height of the bagged product and the tear resistance of the bagged product.
Preferably, in the event that the reactive force detected by the servo motor while the presser unit presses the bagged product is smaller than a predetermined value, an abnormality dealing process is performed. Alternatively or in combination therewith, in the event that the displacement of the presser unit detected by the servo motor during a predetermined time while the presser unit presses the bagged product is greater than a predetermined value, an abnormality dealing process is performed.
Preferably, the servo motor is mounted on a support frame for supporting the transport means at a location below the transport means. This arrangement, that is, the mounting of the servo motor on the support frame at the location below the transport means makes it possible to achieve a maximized utilization of a vacant space available below the transport means.
Also preferably, the presser unit is positioned above the transport means and is supported by a presser support structure in which the servo motor is accommodated. This arrangement is advantageous in that since the servo motor is positioned above the transport means, the presence of the servo motor will not provide an obstruction to cleaning of the space below the transport means, which cleaning may be effected while the belt conveyor and the associated component parts of the transport means are removed therefrom.